It is proposed to maintain a viable murine model for AIDS program using the C57BL/6 mouse as the test host and the molecularly- cloned, replication defective strain (Du5H) of murine leukemia virus as the infectious agent. The progression of immune dysfunctions will be monitored by competitive enzyme- immunoassays for serum IgM levels, mixed lymphocyte culture reactions for the assessments of proliferative response to mitogens and alloantigens, flow cytometric assays of the expression profiles of H-2 antigens on peripheral blood cells, and necropsy findings. The pathogenic modulations of the lymphocyte repertoires of the C57BL/6 and A/J strains of mice infected with Du5H virus will be characterized. An opportunistic infection (OI) model featuring persistent Cryptosporidium parvum infection in murine AIDS (MAIDS) will be established in C57BL/6 mice. The interaction of M. avium and C. parvum with immune responses in MAIDS including the B and T cell subsets will be determined. Lymphocyte functions, especially the role of cytokine, in the progression of the OI will be monitored. The protective values of adoptive transfers of immunity-related cells and nutritional supplementations and the therapeutic efficacies of various regimens including bovine colostrum will be evaluated in the OI model. The mechanism precipitation MAIDS will be investigated by identifying the pathogenic epitope of the major gene product of the Du5H virus. The specific oncogene induced by the virus and the possible roles of oncoproteins and viral proteins in maintaining infection by virus will be investigated. Monoclonal antibodies to meet the specificities described in various protocols shall be generated. The gene that codes for resistance to Mycobacterium spp. from the macrophages of the C.D2 Idh-1/Pep-3 mouse, which expresses the resistance allele, will be cloned and characterized, as this may elucidate the potential for development of gene therapy for this opportunistic infectious agent.